I'm setting up a 55 for my Leo and it will be bio active as I grow cacti and succulents. The base layer of substrate is meduium sized pebble for drainage, then soil, then sand and pea pebbles for the top layer. This will not only be a heavy tank but having to uproot plants is a drag. I was thinking of putting my heat pad on piece of floor tile between the first layer and the soil. There is little chance of the pad ever getting wet as in bulb water my plants. I'll also have Blue Death Feigning Beetles in with her/him dunno yet its still pretty young. Hoping its female and I can add another down the road or maybe add one now and hope for the best. I run 4 T5 grow bulbs that I can regulate the temp and living in Arizona humidity isnt a problem. My tank runs a between 30 -40.